This invention relates to the field of preparing products in tubular casings and enclosing the products in netting. One method generally used in the food industry is to pump food products, such as pasty sausage meat, whole muscle meats, or otherwise, through a product horn. The food products are forced into a tube formed continuously from flat sheets of film. A similar process is used for non-food products, such as caulking material. The flat sheet of film is formed either from roll stock or from fan-folded film.
The film is brought over a forming wire or a forming shoulder to roll the flat sheet into a tube. A pasty mixture is pumped into the tube, which expands as it is filled against a coaxial netting. This process is described in, for examples, U.S. Pat. No. 7,441,386, Apparatus for Forming Tubes in Nets, U.S. Pat. No. 7,063,610, Apparatus and Method to Net Food Products in Shirred Tubular Casing, and U.S. Pat. No. 4,958,477, Apparatus for the Production of Meat Products, the disclosures of all three of which are incorporated herein.
Various types of film are used to create the tube. Common materials used in food products include plastic, collagen, paper, cellulose, and other vegetable products. End users choose the film material based on the end use of the materials, cost of the film, ease of use of the film, custom and practice, and, sometimes, religious considerations. For example, collagen does not have to be removed from a food end product, as it is incorporated into the food during processing. Collagen, however, is made usually from beef hides. Cellulose is relatively inexpensive, but must be removed from a food end product.
Regardless of which material is chosen, the film must be brought over a forming wire and formed into a tube. This process produces friction between the forming wire and the film and causes drag on the film. It is desirable to reduce both friction and drag. One way that has been attempted is to use a plastic roller or plastic beads on the forming wire. This method has not been particularly successful. Another alternative has been to coat the forming wire with a fluoropolymer such as the one sold under the brand name Teflon® by E. I. du Pont de Nemours and Company or its affiliates. The constant motion of film over coated forming wire, however, causes the coating to rub off. Consequently, the forming wire must be removed periodically and sent out for re-coating, which causes downtime in the production process and an added expense.